To think it’s time to scrap the concept of BMI?

[AnyoneWhoHasAHeart]

There’s a lot of talk these days about the obesity crisis, and what a healthy weight should be. And I totally agree that we absolutely are in a place where obesity is definitely a thing.

However, there seems to be very little talk about what is at the other end of the scale, and being. Underweight seems to be a trend people want to aspire to.

I calculated my BMI this morning, and it told me I have a BMI of 21.

I’ve just spent four months in hospital, have had major surgery, and lost an astronomical amount of weight. I wasn’t overweight to begin with, but I am 5ft 2, and I currently weigh 44kg. I don’t need to be told I need to gain some weight at least, and I am trying, but I’ve lost my appetite so that’s a process.

But calculating my BMI this morning it said that my BMI is 21, which is almost at the upper end of the scale, however it then goes on to say that a healthy weight for my stats is between 47/60kg. So how exactly does that follow?

If you’re looking at BMI only you could be forgiven for thinking that 44kg is a healthy weight, when trust me it really isn’t at this point.

So how many people are being told they’re obese based on these types of calculations where actually, they’re probably not?

We Need to start looking at weight not BMI, because it’s just not accurate.

BMI is fine. Yes, it's a blunt tool but one with a wide range.

The healthy weight for my height is between around 7 and a half stone and 10 stone. I'm about 9 and a half. A 2 and a half stone range is big!

I was 8 stone for years as an adult and, tbh, looked ill. Another woman my height would look perfect at 8 stone. So it already factors in things like frame/build.

The average weight/size of people might have increased over the years but that says nothing more than people are getting bigger/heavier. Not that we should abandon the idea or shift the parameters.

Bmi 21 isn't and has never been touted as the upper end of the scale. So whatever the arguments around BMI, your facts are wrong.

It’s a useful indicator for most people unless they are expectionally muscular. You’ve simply entered your information wrong or written it wrong here. Your BMI is in the underweight catergory.

Obviously there’ll be individual differences, and it may need adjusting for different groups (eg older adults as PP suggested), but broadly speaking, something that compares weight and height seems like a good measure. You can’t just look at weight, you need to consider height - like with children where you look at height and weight centiles. And looking at more than height and weight (and population groups like age) would make it more complicated so less useful as a guide that anyone can use to get a general idea of their weight. Obviously there’ll be some differences at the borders of each category - but that’s the same for anything with a cut off (<X is overweight, >X is obese).

And I think most people will know if they are an outlier eg they are extremely muscular and that is what is pushing their BMI up.

I have a wide skeleton so BMI isn’t accurate for me, I was anorexic and it said I was in the middle of healthy/ I could lose another stone.

One point of relevance to the OPs thoughts is there’s less margin of safety at the low end of ‘normal’. I’ve just tried the ‘smart calculator’ linked from the thread I mentioned upthread (for my height, weight and age) - this diagram shows what I mean.

Even though you miscalculated your BMI, I agree that it is a silly tool. It is very vague and doesn't take into account muscle mass or body fat percentage.

A blunt tool is better than no tool. And off the bottom end, which is what this thread is more about, chances are the person doesn’t have enough of either fat or muscle.

Yabu.

Did you use the NHS calculator? Typo in the data you entered?

At the moment I have neither 😱.

Waist to height ratio is accurate and used within the NHS.

BMI isnt perfect, but for most people it is a good indicator. There are outliers to every rule though, people with a high muscle mass etc, but those people tend to already understand their weight better than most. For the average person however, BMI is a good indicator.

However, yes your calculation is wrong, and thinking 21 is high is also wrong. Like any toold, it has to be used correctly to be effective.

I think it can definitely be damaging.

Mine fluctuates and as I'm due to come on my period I'm retaining water. This has pushed me up to the healthy BMI limit for my height. However I much prefer try to look at the overall picture health wise. I rarely drink, I eat a healthy diet and hit all the food groups consistently and I do moderate exercise 2/3 times a week, strength train and walk as much as I can. However I can see why this temporary small weight gain could be difficult for someone with body dismorphia or eating disorders. I definitely think BMI can be a useful tool but a holistic picture of lifestyle is better.

I hope you can regain your strength soon. It’s a pity the thread has been rather diverted by the calculation error, because the basic point you were trying to make is valid - being underweight isn’t healthy, and even being at the lower rather than the higher end of the healthy range can leave you with insufficient reserves if you’re unfortunate enough to be seriously ill.

BMI is fine and works for most people to give a rough idea what to aim for . @AnyoneWhoHasAHeart you have clearly put the wrong details into the calculator as everyone else on the thread is getting 17.7 for your weight/ height when they put in the details you’ve given . When you reach a BMI of 21 you will have added plenty of weight and look just fine .

Very few people have enough muscle mass to appear overweight when they are not as per BMI. BMI works perfectly fine for most people, and if you're a body builder or similar you won't be using BMI to calculate if you're overweight or not!

YANBU as a matter of principle as BMI does not take things like muscle mass and body shape into account, which are more reliable indicators of a healthy weight. Most doctors seem to know this too, so I wish the more accurate height to waist or hip to waist ratios were used instead - because what really matters is how much visceral fat is likely surrounding your heart and other vital organs. But I guess understandably they don’t want the faff or potential upset of measuring a patients waist and body composition scales aren’t always that accurate either (plus can’t be used with pacemakers etc).

However my understanding is that BMI is likely to be more accurate when it indicates you are underweight, so you may be being unreasonable in your particular case.

On another thread about why bmi is flawed, a person used the example of female "gladiators" from the tv show, they are a mixture of power lifters, rugby players, cross fit etc. but I used the height/weight stats available for them online and all but one were still within the healthy bmi parameters. I think 1 was marginally over 25.

It always crops up when BMI is raised that there are vast numbers of people out there who have accidentally built up so much muscle the BMI doesn't work for them, despite having never set foot in a gym lol. People don't realise how hard it is to build that much muscle.

And regardless, even if someone is heavily muscular and BMI overweight, that doesn't counteract the negative impact on knees/joints, heart, of carrying around that much extra weight. It's fine to choose to be a huge bodybuilder and be overweight and happy with it, doesn't negate the health risks.

Which calculator did you use? The NHS one works fine and gives me: Your BMI is 17.7 (underweight) for your information.

Either you made a mistake or used a calculator that is inaccurate. Neither is a reason to get rid of the BMI. The BMI is flawed in some ways but gives it gives a guide. Your reasoning to get rid of it is based on incorrect information.

The height to waist indicator is brutal lol, I'm an hourglass shape and even at 22 BMI I had too much weight around my middle when I calculated it! Something to aim for I guess haha.

Most of the people upset about BMI would get a shock if they moved to height/waist or even worse... fat callipers!

Yikes - I hope this isn't a rather clunky attempt to get people to commend you for being unhealthily underweight. Which BMI calculator did you use for this? The NHS has BMI calculators on its website - use them.

As for BMI being inaccurate in general: it is a guide. There will always be outliers and people who have body types that make the BMI results a bit odd (for example, bodybuilders and those who purposefully develop a lot of muscle).

There has to be some form of easily accessible and usable calculator/measure to give people some starting-point information about whether they are a healthy weight or not: BMI does that. Most people understand that it isn't the be all and end all, just a very very general starting point and point of reference. If you don't like it then don't use it.

As someone said upthread, better a blunt tool than no tool at all. Many people go 'by eye' or clothes sizing to convince themselves that they are still fine (I've done it myself) and there's enough leeway using this method to become really quite overweight without acknowledging it.
BMI isn't perfect, but the act of weighing oneself can sometimes be enough for us to think 'hmm, yes, piling on the pounds a bit here.'

I agree - the body fat measurement systems can be a shock for a lot of people. They are very helpful though - but require more kit and more time to accurately measure, which is something the NHS just doesn't have capacity to do.

Which calculator did you use? I just used the first 5 that came up on google and they all gave me the same result- you’re underweight.

BMI is a good guide tool but it isn’t exact. I don’t think it needs to be scrapped but health care professionals need to exercise common sense. Sometimes they do, sometimes they don’t.